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I think I've read every post here about V-brake squeal, as well as the popular ones on the Sheldon Brown site, the Park Tools guide and so forth - but I seem to have a brake squeal that just won't abate, and I'd like a 2nd (and 3rd and 4th opinion) before I replace the last few components I haven't yet replaced.

I've a Trek 7.3 hybrid bike, around 2009 vintage - it has a 700C Bontrager alloy rim and Avid Single Digit 3 v-brakes (which I believe are OEM only). About 9 months after owning it and riding about 8 kilometres a day 4 days a week it developed a brake squeal at the front - strangely the back brakes have never been a problem and they work really well. "No problem," I thought, and I cleaned the rim (using a steelo/600grit sandpaper) and toed in the brakes slightly - which fixed it adequately, although temporarily. This process is something I've repeated over the last few years - eventually replacing the worn down pads with a few different styles of cartridge pad.

But the squeal has been steadily growing to the point where the I needed stupid amount of toe to stop it - which really just gave me brakes with questionable efficacy. I eventually swapped to a Kool Stop pads - though again this fix was temporary.

Being a 700C wheel, I toyed with going to the style of brakes most road bikes have - but I lack the appropriate mounting hole in the front forks - and the tools with which to make one.

Noting that there was a reasonable amount of play in the bushes on each brake arm (they're integral to the arm), I bit the bullet and ordered a set of Avid Single Digit 7 brakes, to replace the brakes on the bike. Pulling the old brakes off I noticed the brake bosses on the frame appeared to be bent - so I replaced those too. I cleaned the daylights out of the rim, again with steelo, a quick run over with 600grit sandpaper and an application of automotive brake cleaner to remove any oil (it seems to be a lot cheaper than isopropyl alcohol here and appears to work well - also, I had some close at hand). I also make sure I clean the surface of the pads removing any grit and give them a with once-over with a clean bit of sandpaper.

Following a number of guides, I installed and set up the new brakes and they are excellent for the most part; the arms are meatier and have far less flex in them and the return adjustment, and adjustment in general, seems to be easier setup and control.

But they still squeal, loudly - in the dry, in the wet, night and day. And granted, terrifying j-walking pedestrians with the noise can be fun - but I don't think it's doing me any favours.

So given that I've replaced the brake bosses, the brake arms, the brake pads and removed cleaned, re-greased and refitted the forks - that really only leaves the rim.

Do I replace the rim, or do I just deal with the squeaking? Or have I missed something really obvious?


An update on my progress.

Replaced the front wheel with a 2nd hand one in excellent condition (having been recently respoked and trued) - some sort of lightweight Ritchey thing. The wheel had been used by a chap who'd commuted a decent distance on it every day and had had no problems with squeal.

I cleaned the rim with 600 grit glasspaper, then automotive brake cleaner and a steelo, wiped clean with paper towel. I then cleaned it with methylated spirits and again wiped it clean with a paper towel. This removed all the old traces of brake pad grit and oil and let me check that the surface of the rim was flat.

I took off the Avid cartridge pads supplied with the Single Digit 5 brakes and, after cleaning them up with sand paper and a wipe of methylated spirits, put the Koolstop single compound 'orange' pads back on.

Adjusted the brakes to make sure they sat on the rim properly (they're slightly thicker than the Avid pads).

And still it squeals!

Sadly, I'm thinking I just have one of those very resonant frames.

The next step is the replace the forks - but I'm in no rush to that anytime soon give the cost.

I'm still wondering if I've missed something obvious!

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Thanks for tidying up the post/title @NeilFein –  inflammable Aug 9 '12 at 2:42
    
Welcome to the site. This sounds like an amazingly complex situation, I hope we're able to help out. –  Neil Fein Aug 9 '12 at 4:53
    
Sometimes it's easier to just live with a bit of brake squeal. Often it only happens at specific speeds/braking forces - the only fix might be to avoid whatever that is. –  Abhi Beckert Aug 11 '12 at 21:39
    
Well, at present it's anything other a gentle pressure and at any speed < 30kmph - getting louder as I decelerate. So hard to avoid really. –  inflammable Aug 12 '12 at 8:27
    
Now you've discounted the wheel and brake, I guess it's time to start looking at everything else. Are the brake bosses straight and tight? Is the headset greased and properly adjusted? During braking, is there any vibration anywhere? –  Olly Hodgson Aug 23 '12 at 9:31
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1 Answer 1

Is there a chance the rim is wearing out? Have you tried a different wheel? Have you tried toeing the brakes in the opposite direction? It sounds like you've tried just about everything else. I'm leaning towards the wheel being the issue. Otherwise it sounds like the frame is just prone to resonance with the vibration of the brakes. I've got a mtb frame that doest this horribly with the back brake. Several friends have the same frame with different brakes but the same issue. Some frames are just more likely to resonate than others, though it's usually more of a wheel issue with rim brakes.

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Is it worn, very probably, though I have no idea what level of wear to expect from my riding habits! Trying a rim is probably the best idea - I'll see what I can find 2nd hand to test with and move to a new one if that shows promise. –  inflammable Aug 9 '12 at 2:39
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Often there's a deeper groove in the wheel that serves a similar purpose to wear bars on a car tire. For some rims you can dig up minimum rim thicknesses which can be measured with calipers. If your rim has a grooved/machined braking surface and that surface is gone, good chance your rim is shot. Regardless of the braking surface, if there's an indent where the brake pad meets the rim, especially if it's to the point where the rim seems bowed out where it meets the tire, the rim is shot. –  joelmdev Aug 9 '12 at 2:58
    
The rim does indeed have a groove machined into it - though my vernier calipers have a narrow enough section to measure it - it seems to have some depth to it. No obvious signs of wear, but I'll put something flat and straight on it and see. Thanks! –  inflammable Aug 9 '12 at 10:12
    
If you change the rim, your pads won't "wear in" until you've done quite a lot of riding on it. Until then, you won't know if it's fixed or not. –  Abhi Beckert Aug 11 '12 at 21:42
    
Good to know - thanks. –  inflammable Aug 12 '12 at 8:26
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